The present invention relates to an evaporator suitable for use in a car air conditioner, which is a refrigeration cycle to be mounted on an automobile, for example.
In this specification and appended claims, the upper, lower, left-hand, and right-hand sides of FIGS. 1 to 4 will be referred to as “upper,” “lower,” “left,” and “right,” respectively, and a direction represented by arrow X in FIGS. 1 and 2 will be referred to as an “air-passage direction.”
An evaporator of such a type has been known (see Japanese Patent Application Laid-Open (kokai) No. 2009-156532). The known evaporator comprises leeward and windward tube rows each of which is composed of a plurality of heat exchange tubes disposed such that their longitudinal direction coincides with the vertical direction and they are spaced from one another in the left-right direction, and which are disposed side by side in the air-passage direction; leeward upper and lower headers with which upper and lower end portions of the heat exchange tubes of the leeward tube row communicate, respectively; and windward upper and lower headers with which upper and lower end portions of the heat exchange tubes of the windward tube row communicate, respectively. In the two tube rows, descending flow tube groups each of which is composed of a plurality of heat exchange tubes and in which refrigerant flows from the upper side toward the lower side and ascending flow tube groups each of which is composed of a plurality of heat exchange tubes and in which the refrigerant flows from the lower side toward the upper side are arranged alternately. The leeward tube row includes three tube groups, and the windward tube row includes two tube groups. A refrigerant inlet is provided at one end of the leeward upper header, and a refrigerant outlet is provided at one end of the windward upper header, which one end is located on the same side as the side where the refrigerant inlet is provided. In the leeward tube row, a nearest tube group which is the nearest to the refrigerant inlet and a farthest tube group which is the farthest from the refrigerant inlet are descending flow tube groups in which the refrigerant flows from the upper side toward the lower side, and an intermediate tube group between the two descending flow tube groups is an ascending flow tube group in which the refrigerant flows from the lower side toward the upper side. In the windward tube row, a nearest tube group which is the nearest to the refrigerant outlet is an ascending flow tube group in which the refrigerant flows from the lower side toward the upper side, and a farthest tube group which is the farthest from the refrigerant outlet is a descending flow tube group. The farthest tube group of the windward tube row is disposed on the windward side of the farthest tube group of the leeward tube row, and the two farthest tube groups constitute a single path. An upper end portion of the farthest tube group of the leeward tube row and an upper end portion of the intermediate tube group located adjacent to and upstream of the farthest tube group in the flow direction of the refrigerant communicate with one leeward compartment which is provided in the leeward upper header and which is closed at opposite ends thereof. An upper end portion of the farthest tube group of the windward tube row communicates with one windward compartment which is provided in the windward upper header, which is closed at opposite ends thereof, and which is shorter in length in the left-right direction than the leeward compartment. The entire leeward compartment and the entire windward compartment constitute a single space, and a refrigerant passage section is provided so as to establish communication between the windward compartment and a portion of the leeward compartment with which the farthest tube group communicates. The refrigerant having flowed into the leeward compartment from the intermediate tube group of the leeward tube row flows toward the farthest tube group side of the leeward compartment, flows downward within the heat exchange tubes of the farthest tube group. Simultaneously with this, the refrigerant having flowed into the leeward compartment from the intermediate tube group of the leeward tube row flows into the windward compartment through the refrigerant passage section, while flowing toward the farthest tube group side of the leeward compartment, and then flows downward within the heat exchange tubes of the farthest tube group of the windward tube row.
In the case of the evaporator disclosed in the above-mentioned publication, in the leeward compartment of the leeward upper header, the refrigerant having flowed from the intermediate tube group of the leeward tube row into the leeward compartment and having flowed toward the farthest tube group side of the leeward compartment flows more easily into the heat exchange tubes of the farthest tube group of the leeward tube row than into the descending flow tube group of the windward tube row through the refrigerant passage section. As a result, the amounts of the refrigerant flowing through the heat exchange tubes of the two farthest tube groups forming the single path become non-uniform.
Therefore, in order to improve cooling performance, it is desired to equalize the amounts of the refrigerant flowing through the heat exchange tubes of the farthest tube groups of the leeward tube row and the windward tube row which are the same in terms of the flow direction of the refrigerant within the heat exchange tubes.
Incidentally, there has been known an evaporator in which the leeward upper header and the windward upper header are provided by dividing the interior of a single tank, in the air-passing direction, into two spaces by a partition portion extending in the left-right direction and a refrigerant passage section for establishing communication between the windward compartment and the region of the leeward compartment with which the farthest tube group communicates is formed by removing the partition portion over the entire length of the windward compartment (see Japanese Patent Application Laid-Open (kokai) No. 2015-157507).
In the evaporator disclosed in Japanese Patent Application Laid-Open No. 2015-157507, refrigerant flows more easily into the windward compartment through the refrigerant passage section than into the descending flow tube group in the leeward tube row, which group constitutes the above-mentioned single path, whereby it becomes easier for the refrigerant to flow into the descending flow tube group in the windward tube row, which group constitutes the above-mentioned single path. As a result, the amounts of refrigerant flowing through the heat exchange tubes of the farthest tube groups of the leeward tube row and the windward tube row can be made uniform. However, the amount of refrigerant flowing through the descending flow tube group of the windward tube row, which group constitutes the above-mentioned single path, may become greater than the amount of refrigerant flowing through the descending flow tube group of the leeward tube row, which group constitutes the above-mentioned single path. In addition, the withstand pressure of the tank having the leeward upper header tank and the windward upper header tank may decrease.